During the course of a surgical operation on a patient, it is often necessary to remove from the site of the operation various body fluids, tissue, and debris or fluids that have been injected. For example, a number of surgical operations utilize an irrigation inflow system which is used in the surgical operation, such as arthroscopic surgery, for providing irrigation fluid to the joint to distend the joint sufficiently to visualize and operate in the joint space arthroscopically, to provide sufficient pressure to tamponade internally any blood vessels compromised which may bleed, and also, to lavage the joint to remove debris.
During arthroscopic surgery, other devices are often utilized. These devices include an arthroscopic shaving system of which the shaving blade functions by rotating and cutting fragments of loose debris in the joint, and by providing a cannulated and integral means of removing this fragmented shaven debris. The shaver handpiece contains at its distal end, an attachment barb, that can be connected via suction tubing to the operating room's vacuum/suction system. In the process of removing this debris, the vacuum is activated and pulls the debris through the cannulated shaver blade and out of the joint space.
The vacuum system may be unregulated and the full effect of the vacuum can be applied to the joint via the suction tubing to the shaver blade. When this occurs, the pressure in the joint space may decrease. Depending upon the patient's condition and the capacity of the irrigation pump system, the resultant pressure in the joint space may or may not be sufficient to maintain distention and to tamponade any bleeding vessels. Oftentimes, the resultant pressure in the joint space decreases, as more fluid is withdrawn from the joint, than that which can be infused, thus creating a deficit. When the pressure in the joint decreases to below that of the exposed, compromised blood vessels, the vessels can potentially bleed.
It is therefore important that the proper level of negative pressure is applied to the suction line over the course of the surgical operation since inadequate or excessive negative pressure within the suction line can lead to complications. Over distention of the operative space is not desirable since it can lead to complications of a serious nature and therefore, the suction line is used to withdraw fluid, debris and the like from the operative space. Conversely, it is not desirable for the negative pressure in the suction line to become excessive since this leads to a different set of complications, namely, those noted above.
In order to prevent these complications from occurring, it has been found beneficial to install a relief valve between the vacuum source and the surgical device in order to control the amount of vacuum that is applied to the operative site. It is known to place a vent in the suction line so that the surgeon can limit the negative pressure within the suction line by opening the vent. In other words, such suction control usually consists of a valve that can be adjusted to admit a certain flow of ambient air into the suction line, thereby reducing the suction force at the surgical device. For example, in an arthroscopic operation, the suction line is connected between a vacuum source and the shaving device. During the arthroscopic operation, the surgeon will activate the suction line to withdraw fluid and debris away from the operation site through the suction line and use the vent or valve mechanism to effectively maintain the desired amount of negative pressure within the suction line.
There are a number of valve mechanisms available for venting the suction line. For example, in some suction devices, the air intake of the regulating valve is controlled by the position of the surgeon's finger over the air intake. Unfortunately, this type of device is very cumbersome to operate since it requires the surgeon to place and maintain his or her finger over the air intake. If the surgeon's finger should be become slightly displaced as by a slipping action or the device itself slips, then the air intake is opened and ambient air rushes through the valve and into the device. This results in the suction being reduced or completely interrupted.
Many of the other types of valve mechanisms that are used are of an “on/off” type. In other words, the vent is either fully opened or fully closed. The disadvantage with this type of arrangement is that it does not offer the variability that is often desired in venting the negative pressure (suction force) in the suction line. In other words, the optimum venting might be a condition between the “on” position and the “off” position of the vent.
An adjustable type valve is generally disclosed in U.S. Pat. No. 5,531,712 to Malcolm et al. In this patent, a relief valve for regulating the suction of an endoscope includes a plunger which can be screwed into a fluid escape channel. At one end thereof, the plunger includes a conical tip that is shaped and dimensioned to progressively obstruct an escape port, in combination with longitudinal grooves along the threaded walls of the plunger. Thus, the patent only teaches adjusting the air flow through the escape port by adjusting the plunger. There is no teaching or suggestion of incorporating a second valve element to be used with the plunger to further provide variability of the valve.
It is therefore desirable to provide a relief valve mechanism that not only vents the suction line to ambient air under prescribed conditions but also has a mechanism that controls the vent in view of negative and positive pressure build ups in the suction line.